We have previously found that regulatory T cells and myeloid-derived suppressor cells infiltrated into the liver of female mice following halothane treatment and appeared to have tolerogenic activity preventing halothane to cause an adaptive immune response against the liver. This year we report that several other potentially tolerogenic cells enter the liver after halothane treatment. Conclusion: These findings suggest that multiple tolerogenic cells play a role in preventing drugs from cause adaptive immune reactions against the liver. Blocking the activities of these cells may allow the development of animal models for testing the potential of new for causing adaptive immune toxicities against the liver.